Earthworm sterols include two, present in high concentration, capable of sensitizing singlet oxygen and reacting with it to yield a variety of substitution products. We have developed HPLC procedures to separate and monitor these reaction products. Characterization of the products has required high resolution (500 Mhz) proton NMR, infrared, UV-visible, fluorescence and mass spectrometry. We have raised earthworms in the laboratory through four generations, and are beginning selective breeding procedures to eventually establish a reasonably homozygous laboratory strain of Eisenia.